Could be, I'm not that far along. West Marine Catalog shows their house brand at 105. Problem I've had with 12 v batteries has been that with 4 in parallel, one is "weaker"somehow and sucks up all the charging amps till it burns out. 2 pair of 6v golf carts in series has not done this to me.
Bill,
Some thoughts.
1-If you had a 12V go bad this can happen in any battery system, 6 or 12 volt. The important thing is that when you upgrade, or add to a bank, you should always replace all the batteries so as not to mix batteries of differing ages.
2- Individual batteries are made up of, well, individual batteries or internal cells. 6v batteries essentially have three internal 2v batteries and 12 volt batteries have six internal batteries 2v batteries.
3- When you combine in parallel or series/parallel you are essentially connecting all these internal batteries externally. While this is not a bad idea by any means, it does mean old and new or batteries of different type should not be mixed and matched.
4- Three 12v batteries is not a bad set up, if that is what you have the space for. The Trojan SCS 225 is an amazing battery and offers 125 Ah's.
5- How many Ah's do you need? Have you run the numbers? If you have run the numbers how did you determine actual daily consumption? Do you have a battery monitor?
6- The rule of thumb, when sailing off the dock & beginning with a full charge, is that you will have 50% of the total Ah capacity to use before hitting a 50% depth of discharge. For battery longevity and cycle life you don't want to regularly discharge below 50% of the total bank capacity.
7-The rule of thumb when sailing off the hook, with only an alternator, is that you will only ever recharge to about 80% of capacity. So if you have a 400 Ah bank you would only have 320 Ah's of capacity and then only 120 Ah's of usable capacity before you hit a 50% depth of discharge on the banks face value of 400 Ah's..
8- I have found it is easier, and possibly even less expensive up front, to minimize my consumption. LED interior lighting, LED running and anchor lights, using DC power for computers/TV's as opposed to inverting to 120 V then stepping back down to DC anyway. We have a 36 footer and use lots of lighting, a stereo, electronics and my daughter watches about an hour of TV a night and we still never draw our 240 Ah bank even near 50% DOD. So there are two ways to go, bigger bank with more complexity, expensive wire runs etc., or a slightly smaller bank and less consumption.
9- If you reside at a dock and you use refrigeration leave it on during the week and leave some mass in it, such as gallons of water, so the box is pre-chilled before you leave the dock. This can save a massive amount of Ah's in the energy needed to cool all the materials in the ice box. You are not just cooling the air, but all that fiberglass too. The fridge on our old Catalina would cycle at about 80% + on during the first day or two out but if I had a chance to leave it on full time we would cycle at about 50%-60% on with a 5 amp draw that is a significant Ah savings..
Lots of ways to go, but I would not rule out banks of 12v batts just because of one failure. While I do personally prefer 6V batts there is nothing wrong with a good 12 v deep cycle battery. I currently have a 12v bank due to space constraints and actual need. If you can get away with three 125 Ah 12v batts that would save you a significant amount of money in wiring.
When combining batteries you'll want as large a cable as you can get as they are often called upon to deliver starting loads of up to 150 amps, sometimes more.. For a separated 6V in the v-berth, that may have ten feet of wire in each direction, I would personally use 3/0 wire to attain a 2% voltage drop or 1/0 wire for 3%..
